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A tsunami is a series of waves most often caused by an earthquake beneath the sea floor. If a large earthquake displaces the sea floor near Washington's coast, the first waves could hit the shore within minutes. The waves can kill and injure people and cause severe property damage.
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Tsunamis have hit Washington's coast
- 1964
An earthquake in Alaska triggered a tsunami that reached a height of almost 13 feet (4 meters) at Seaview, Washington.
- 1700 A powerful earthquake (magnitude 8 to 9) and tsunami hit Washington's coast 300 years ago.
Every 300 to 600 years
Great earthquakes (magnitude 8 to 9) and tsunamis have repeatedly rocked the Pacific Northwest. Catastrophic earthquakes and tsunamis have occurred along Washington's coast at least six times in the past 7,000 years -- about every 300 to 600 years. There is a good chance that another earthquake will occur offshore within the next 100 years.
When and where tsunamis occur
Tsunamis can occur at any time of the day or night, under any and all weather conditions, and in all seasons. Beaches open to the ocean, by bay entrances or tidal flats, and the shores of coastal rivers are especially vulnerable to tsunamis.
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Dead trees: evidence of past tsunamis
Dead trees on Washington's coast record a giant earthquake and tsunami that occurred in 1700, one hunded years before Lewis and Clark reached the mouth of the Columbia River. Dead forests can indicate a sudden sinking that occurs with major earthquakes. By examining tree ring patterns and by carbon-14 dating, geologists have determined that the last big coastal sinking occurred about 300 years ago.
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Washington's coast at risk:
an offshore fault
Not all earthquakes cause tsunamis, but many do.
When an earthquake occurs under or near the ocean, the risk of a tsunami increases. One of the largest active faults in North America, the Cascadia Subduction Zone,
runs parallel to Washington's coast, 32 to 70 miles offshore. This fault, researchers say, will cause another giant earthquake and tsunami.
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In the event of a tsunami
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Consider an earthquake a warning. A sudden drop or rise in sea level may be a tsunami approaching.
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Head for higher ground immediately.
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Never go to the beach to watch a
tsunami come in. If you can see the wave, you are too close to escape.
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Do not return to the beach after the first tsunami wave hits.
Waves may arrive for several hours.
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Wait for word from authorities. Stay tuned to your radio, marine radio, or NOAA Weather Radio.
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Tsunamis, Washington State Military Dept, Emergency Management Division.
Tsunamis and safety tips for Washington's coast -- including tsunami evacuation routes.
Tsunamis,
Federal Emergency Management Agency.
What to do before, during, and after a tsunami.
Tsunami!, University of Washington, Geophysics Dept.
An comprehensive tsunami information resource.
Tsunamis and earthquakes, USGS.
Tsunami research, animations, and a model of a potential tsunami striking the Pacific Northwest coast.
Life of a Tsunami, Western Region, Coastal and Marine Geology, USGS
How tsunamis form; diagrams and descriptions.
Tsunamis, The Pacific Tsunami Museum
Tsunami pictures, stories, memories, and answers to frequently asked questions.
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